One-pot catalytic transformation of olefins into cyclic carbonates over an imidazolium bromide-functionalized Mn(III)-porphyrin metal-organic framework

摘要

The direct synthesis of cyclic carbonates from olefins involves epoxidation and CO2 cycloaddition reactions in series. It is, however, a challenging task to devise single catalyst with the multiple functions for one-pot reaction. Herein, an imidazolium bromide ionic liquid-functionalized metalloporphyrin ImBr-MOF-545(Mn) was proposed as an effective catalyst for the reaction. The effects of temperature, pressure, catalyst loading, and time were examined for individual reactions and finally for one-pot reaction. ImBr-MOF-545(Mn) was efficient under solvent-free condition of 60 degrees C, 5/5 bar (O-2/CO2), and 10 h. The Mn(III) ions with the dual functions of oxidation and acting as Lewis acid catalyst with strong nucleophilic/leaving bromide anion in an adjacent position of mesoporous MOF-545 resulted in high efficiency and selectivity to the cyclic carbonates. The catalyst also showed sufficient stability for up to 5 runs with little decline in catalytic activity. A radical mechanism for the epoxidation step and a plausible reaction pathway was proposed.